Sporting clashes between New Zealand and Australia will always feature the teasing and banter that is part and parcel of an intense rivalry. Little brother New Zealand takes the opportunity to exercise the chip on his shoulder, while Australia and its supporters always bring a swaggering self-confidence to such occasions.
Something is sadly wrong, however, when this rivalry moves beyond good-natured ribbing, and Australian fans are spat at and verbally abused. Rugby NZ 2011 chief Martin Snedden was guilty only of understatement when he pronounced himself "very disappointed" at incidents during and after the Wallabies' loss to Ireland at Eden Park last weekend.
The reasons for this outbreak of anti-Australian hostility by a sizeable minority of the New Zealand spectators at the game are not hard to discern. Successive World Cup failures since 1987 have caused some All Black supporters to abandon a sensible perspective.
They have become obsessed with winning on home soil this year. In that context, Australia is widely regarded as the major obstacle, particularly since its Tri-Nations win over New Zealand in Brisbane.
In its own peculiar way, the animosity is a sort of backhanded compliment. Players such as Quade Cooper, Will Genia and Kurtley Beale are feared. Cooper has also created a rod for his own back by initiating skirmishes with the All Black captain, Richie McCaw.
Explanations, however, are not excuses. Nor is it reasonable to justify the behaviour of the spectators by pointing to the abuse sometimes heaped on New Zealand teams and their supporters across the Tasman. Of course, Australian crowds cannot claim innocence in this respect. They, similarly, reserve their most ill-natured barbs for opponents they rate. Richard Hadlee, for one, felt the full wrath of spectators in the likes of the notorious Bay 13 at the Melbourne Cricket Ground. Two wrongs, however, will never make a right.
Some of the behaviour at Eden Park was doubtless fuelled by alcohol. All of it was fuelled by ignorance. The little brother complex aside, it will always be odd that New Zealanders abuse Australians when the ties between the two nations, many of them forged on battlefields, run so deep.
Equally, whenever New Zealanders and Australians find themselves in a foreign country, they gravitate towards each other. The similarities in character and the things in common far outweigh the differences. It is tempting to assume that those who acted so spitefully at Eden Park are blighted by insularity and have never experienced this camaraderie.
Mr Snedden has described the behaviour as "out of character" for New Zealanders. He is only partly right. Crowd conduct at Eden Park towards visiting teams has undoubtedly deteriorated over the years. Just one example is the booing of goal-kickers. There was a time when their efforts were accorded a respectful silence. As the level of booing increased, park officials attempted to turn back the tide. This proved futile, and their beseeching messages were eventually abandoned.
Examples of extreme bad behaviour do not go unnoticed overseas. Such is the way in an era of instant personal communication. If this country wants to be remembered for the friendliness and conviviality of its welcome to all overseas visitors during the World Cup, it is important that such behaviour does not linger. A minority of New Zealanders need to understand the difference between good-hearted banter and disgraceful abuse. If they don't, those sitting or socialising around them should let them know.